Prior to setting forth the background of the invention, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “Wi-Fi” as used herein is defined as any wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards.
The term “Access Point” or “AP” as used herein is defined as a device that allows wireless devices (also known as User Equipment or “UE”) to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself.
The term “client” as used herein is defined as any device that has wireless communication capabilities, specifically, the IEEE 802.11 standards. A client may be for example a smart telephone, a laptop, a tablet or a personal computer (PC).
The term “node” as used herein is defined as general name for both IEEE 802.11 AP and IEEE 802.11 STA.
The term “CSMA/CA” stands for Carrier-Sense-Multiple-Access/Collision-Avoidance, representing a requirement to listen before transmitting in a multi-node wireless system that shares a common channel on the basis of first-come-first-served.
The notation “SINR” stands for Signal-to-Noise and Interference.
The term “time division duplex” (TDD) as used herein is referred to in general for systems using the same frequency spectrum for methods of communications in a time division manner such as Wi-Fi systems.
While Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE) multi-channel Time-Domain-Duplex (TDD) base stations typically synchronize transmitter/receiver time interval amongst themselves, in order to avoid self-jamming, the Wi-Fi 802.11 protocol does not normally lend itself to such synchronization, since it is a contention based, Carrier Sense Multiple Access (CSMA) based protocol that practically requires independent transmitter/receiver switching for each channel.
Similarly, Wi-Fi clients will avoid transmitting over a channel that is not completely silent, thus allowing even the faintest of signals coming from co-channel neighboring APs and clients, to interfere with timely acknowledgements, generating unjustified retransmissions, which significantly reduce efficiency and effective capacity.
All of the above has therefore been dependent on significant isolation between Wi-Fi cells, a condition that suits indoors applications, where walls attenuation plays a positive role.
Recently however, Wi-Fi outdoors deployments have become a new trend, introducing new challenges in frequency reuse and capacity.